This invention relates to the art of casting concrete pipe, and more particularly to a novel apparatus for pouring concrete into a vertically oriented pipe mold.
In the manufacture of certain types of large-diameter concrete pipe, for instance pipe having a diameter as wide as 20 feet, concrete is poured into a vertically disposed pipe mold comprising a cylindrical outer mold case and a cylindrical inner core. In most instances, the pipe is reinforced with a relatively thin-walled cylindrical steel shell, or cylinder, which is disposed in the pipe mold between the outer mold case and the inner core and becomes embedded in the pipe wall when concrete is cast in the pipe mold. The top of the cylinder generally is provided with a spigot-type end ring. When the concrete is poured into the annular space between the mold case and the cylinder, the top level of the concrete is "foreshortened" to form a flat annular end section which is spaced below the spigot ring so that during use, the spigot ring of the pipe can be joined with a cooperating bell-type end ring of an adjoining concrete pipe section.
In some instances, concrete pipe is cast as a straight pipe section in which the spigot ring and the foreshortened annular end section of the pipe lie in separate horizontal planes. In other instances, concrete pipe is cast as a beveled pipe section in which the spigot ring and the foreshortened annular end section lie in planes which are inclined relative to the axis of the pipe.
In the conventional method of casting concrete pipe, a "tamping top" is mounted on top of the pipe mold. The tamping top includes a "spigot round-up ring" engaged with the spigot ring to hold the top of the reinforcing cylinder in a fixed position, and a ring-shaped "halo bar" engaged with the top of the outer mold case to hold the case in a fixed position and maintain equal spacing between the reinforcing cylinder and the mold case. The tamping top forms a continuous annular opening between the cylinder and the mold case through which concrete is to be poured. Once the tamping top is in place, an inverted conical-shaped "pouring cone" is placed above the center portion of the tamping top. Concrete is then emptied from a bucket onto the top of the pouring cone which distributes the concrete evenly through the annular opening in the tamping top. The pouring cone also evenly distributes concrete to the annular space between the cylinder and the inner core. The space between the outer mold case and the cylinder generally is overfilled above its desired elevation, and after the pouring cone is removed, excess concrete at the top of the mold is then dug out by hand, measured with a depth gauge, and hand-troweled to provide a flat, properly leveled annular end section for the pipe.
The job of hand-finishing the foreshortened annular end section of the pipe is a time-consuming and costly process, particularly because of the large size of the pipe, and because the finished end section of the pipe must meet relatively narrow tolerances. Beveled pipe in particular is laborious and costly to finish. The pipe form for beveled pipe generally is overfilled to form a horizontal annular end section, and the excess concrete on the low side of the bevel is then dug out and finished to the desired bevel by offset measurements which require substantial time and effort by the workmen.